One of the more challenging aspects of biomedical therapy has been the treatment of diseases and conditions caused by blood clotting. The mechanism of blood clotting itself is complex, and is caused by the action of plasmin, a hemolytic enzyme, on fibrin and fibrinogen. This action produces various peptide proteolytic products, which cause vascular endothelial damage, hypoxemia, tachyphea, lung vascular injury, and so forth. In addition, fibrinolytic activity has been shown to be associated with cancer, while fibrin degradation products are believed to be produced by extracellular breakdown of fibrin by malignant cells. It has also been hypothesized that fibrin degradation products may be implicated in invation and metastasis of cancer tumors. These products have also been shown to be involved in neovascularization of tumors.
Myocardial infarctions are also recognized to be associated with elevations of fibrin degradation product content.
All of the above conditions, as well as acute thromboembolic events, venous and arterial thrombosis, intracardiac thrombosis, and systemic embolism, are conditions which are difficult to manage. Medical therapy for treating these conditions may, and usually does, involve anticoagulation therapy. One approach is to stop the underlying process of fibrinolysis, and to then rely on normal physiologic mechanisms to restore blood flow and to limit the extent of vascular obstruction or destruction of tissue.
The fibrinolysis process is fairly well known. Briefly, plasmin or plasminogen binds to fibrin, following induction by a plasminogen activator. Thorsen, Biochim. Biophys. Acta 393: 55-65 (1975); Lejnen, et al. J. Biol. Chem. 255: 10214-10222 (1980); Sahata, et al. J. Clin. Invest. 69: 536-542 (1982); Aoki et al., Blood 62: 1118-1122 (1983). Structures in the plasminogen molecule known as lysine-binding sites are involved in this binding reaction. Thorsen, supra; Wiman, et al., Thromb. Res. 10: 213-222 (1977).
Interference with the mechanism has been the goal of research in the field. Two glycoproteins are known to be involved with inhibition of plasminogen-fibrin binding. The plasmin inhibitor ".alpha..sub.2 " has been reported by Moroi, et al., J. Biol. Chem. 251: 5956-5965 (1976). It has been identified as a prime plasmin inhibitor in humans. Mullertz, et al., Biochem. J. 159: 545-553 (1976), and is recognized as a glycoprotein. Gonias, et al., J. Biol. Chem. 23: 14682-14685 (1983); Matsuo, et al., Thromb. Res. 27: 555-562 (1982); Gramse, et al., Hoppe-Seyler's Z. Physiol. Chem. 365(19): 19-26 (Jan. 1984); Ichinose, et al., Biochim. Biophys. Acta 706: 158-164 (1982).
An additional plasmin inhibitor has also been recognized, the Histidine-Rich Glycoprotein (HRG). Lipner, et al., J. Biol. Chem. 255: 10214-10222 (1980); Lijnen, et al., Biochim. Biophys. Acta 742: 109-115 (1983). Its relationship to .alpha..sub.2 has been studied. Ichinose, et al., Thromb. Res. 33: 401-407 (1984).
Additional plasmin inhibitors have been discovered as well. Fazleabas, et al., J. Biol. Chem. 257(12): 6886-6897 (1982), teach a progesterone modulated plasmin inhibitor, identified as a protein. Sumi, et al., Enzyme 30: 252-258 (1983), teach formation of plasmin inhibitors by cyanogen bromide treatment of urinary trysin inhibitors. Levin et al., J. Clin. Invest. 74: 571-580 (1984) suggest that aspirin may have a role in plasmin inhibition.
U.S. Pat. No. 3,000,787, discloses a heparinoidic factor isolated from mammalian duodenum. The methods by which the factor is obtained indicate that the factor is an aminopolysaccharide, or a glycoprotein.
U.S. Pat. No. 3,181,996, discloses a heparinodic factor obtained from the pancreas. Again, the teaching indicates that the extract is a glycoprotein, or an aminopolysaccharide.
U.S. Pat. No. 3,985,871, discloses pharmaceutical compositions using the two factors, disclosed supra, in suspensions of fats, alkyl esters, and aliphatic acids.
This survey of the art shows that there is no teaching or suggestion that lipid containing molecules have plasmin inhibitory activity.
Recently, studies have been undertaken of lipid containing extracts of the mammalian omentum. See, e.g., copending U.S. application Ser. No. 782,724. These extracts have been found, unexpectedly, to be involved in numerous hemolytic physiological functions including plasmin inhibition. What is particularly surprising about the role of these lipid containing molecules is the fact that, in spite of considerable research in the field, only proteins, and glycoproteins, have been found to be plasmin inhibitors.
Plasmin is related to other protein associated enzymes, such as serine proteases, collagenases, etc. The interrelationship of these enzymes is not clear, although one factor that may be common to all of them is the need for metal ions as coenzymes.
It is an object of this invention to provide novel compositions which contain lipid containing molecules with plasmin inhibitory properties.
It is a further object of this invention to set forth methods of treatment of diseases and conditions associated with fibrinogen degradation products, by application of the new compositions.
It is a still further object of this invention to provide new uses for old lipid containing compositions, which have now been unexpectedly found to have plamin inhibitory properties.
How these and other objects of the invention are accomplished will be seen in the accompanying details, which now follow.